Water & Atmosphere 16(4) 2008 NIWA 14 Water & Atmosphere 16(4) 2008 Photo: Mike Martin W e’ve all heard the expression “happy as a clam” *, but how happy can a clam be, especially one living in a contaminated urban estuary? While it seems silly to attempt to measure the happiness of a clam, the larger topic of shellfish health – and the health of their surroundings – is an important environmental issue. We all want healthy estuaries and kai moana, but how do you measure the health of an estuary and its inhabitants? And what indicators distinguish healthy estuaries from degraded ones? Answering these questions is the goal of ‘Estuarine Ecodiagnostics’, a four- year research programme involving scientists from NIWA and the University of Waikato. How do we measure ecological health? Just as there’s no single indicator that summarises a person’s health, there’s no single ecological measure that conveniently sums up the health of an entire estuary. Instead we must piece together the diagnosis from different streams of evidence. For example, we might measure the concentrations of certain contaminants such as trace metals or hydrocarbons in the water or sediment for a picture of pollution levels. Similarly, we can analyse tissues of organisms that live there for presumed contaminants. We might, furthermore, assess the Ecodiagnostics: biomarkers of shellfish health in urban estuaries presence or absence or count the number of organisms or species inhabiting a certain site. We can then compare these findings with benchmark values to rank the relative health of a particular estuary. Ecological and chemical monitoring are very sensitive and useful tools for describing trends in estuarine health over time. But what if we want to find exactly what is stressing organisms? For example, how can we determine whether the generally lower numbers and smaller size of shellfish observed in urban estuaries are the result of chemical contamination or, rather, other environmental factors, such as sedimentation, over- harvesting, or habitat destruction? Unlike the health of an individual person, ecological health spans many time and size scales, ranging from individual cells and individual organisms to populations and species assemblages (or communities). Each biological level tells us something about the health in an estuary, but it doesn’t tell * This saying appears to have originated in the United States in the mid 1800s, and makes more sense in the full version, now rarely heard: ”as happy as a clam at high water”. Water Quality Biomarkers make their mark Ecodiagnostics investigates exposure to • enviromental stress over a range of biological scales. Biomarkers are measurable responses at the • biochemical and organism level. Scientists are measuring biomarkers in cockles • to detect exposure to chemical and metal contamination in estuaries. Michael Ahrens describes the search for environmental indicators that can highlight problems for kai moana.